Electric clock



Aug. 10, 1937. F. ,OEFFLER 2,089,280

ELECTRIC CLOCK Filed Jan. 50, 1932 2 Sheets-Sheet 2 FRc-rz Lne FfLe RlNvENroR- ATTO R N EY- Patented Aug. 10, 1937 UNITED STATES PATENTOFFICE 4 Claims.

'I'his invention relates to electrically driven clocks of the typewherein the driving motor operates intermittently to store up energy ina spring which serves to drive the clock escapement mechanism and hands.

It is an object of my invention to provide an improved and simple formof electric motor drive of the intermittently operating type which isarranged to apply at all times a substantially smooth and uniformdriving torque to the gear trains and escapement mechanism of the clockworks.

More specifically, it is an object of my invention to Iprovide a clockdriving motor which is very simple in construction and operation and tofurnish between the moving element of the clock motor and the driveshaft of the clock Works a driving connection of uniform resiliency,which is supplied with small amounts of energy at short intervals oftime whereby a uniform driving eiect upon the clock works is obtained.

An object of the present invention is the provision of an improved clockmotor which is adapted to produce intermittent power impulses ofrelatively great strength from a small amount of energizing current, andwhich is adapted to function over a very wide range of voltage.

Another object is the provision of a Commutating mechanism or switch,for supplying intermittent electric impulses to a motor, which has fewparts, is easy to assemble and in which the contact points are keptclean by wiping action.

A further object is the construction of an electric clock of theintermittent impulse type, using an electric motor to tension a drivingspring, wherein the clock escapement and gearing comprise a single timeunit, and the driving motor a separate unit, the two units being mountedin axial alignment and having substantially a common center.

Still another object is the provision of an electric clock which isadapted to continue operating for a vperiod of time after the current isturned off, and to continue normal operation when the current is turnedon.

In accordance with my invention, the electric clockv motor comprises amagnetizing coil, a toothed rotor. of magnetic material positionedadjacent to said coiland coaxially'therewith, and a plurality of bars orpole pieces of magnetic material are arranged in magnetic relationshipwith said coil and said rotor. The coil, rotor and role pieces. are heldin proper working relationship by any suitable means, suci. as a frameof non-magnetic material, and a commutating mechanism is provided forintermittently energizing the coil to produce a turning movement of said rotor. This movement of the rotor isopposed by a tension spring thatserves to store mechanical energy which is gradually expended in drivingthe associated time unit. The commutating mechanism preferably consistsof a Contact cam having a brush spring pressed into engagementtherewith, and a lifting finger adapted to be operated, responsive toturning of the rotor, quickly to lift the brush free from the contactcam.

The clock escapement, gears, dial and other parts are assembled in asingle unit, to which the electric motor unit is arranged to be attachedby screws or other holding means.` The motor unit, being entirelyseparable from the time unit, may be disengaged therefrom withoutdismantling either individual unit. So repairs may-be quickly and easilymade; it being merely necessary to remove the holding screws to changethe motor unit.

The commutating mechanism or switch is mounted at one side of the motor,preferably the side away from the time unit, so that adjustments andrepairs may be effected quickly and easily without separating the twounits. A

A preferred embodiment of the invention will. now be described withreference. to the drawings.'

In the drawings, Figs. 1 and 2 are cross sections along lines l-l andl2---2 of Fig. 3;

Figs. 3 and 4 are top and bottom plan views of the electrical equipment;

Fig. 5 is a modification of Fig. 1;

Fig'. 6 is a bottom plan view of the clock. mechanism;

Figs. '7, 8 and 9 are enlarged top plan views of the switching mechanismin various positions; and Fig. is a vertical cross section of theswitching mechanism. I

The electrical elements of the clock are con tained within a molding ofinsulating material I provided with a circular groove 2. Six U-shapedelements constituting the magnetic fleld pieces of the stator arefrictionally held within groove 2 equally spaced from one another. Theends 4 constituting the pole faces of magnets 3 project beyond the wall5 of the molding. The coil 6 of the. stator structure is in the form ofa toroid and is held within the groove 2 by means of brass or othernon-magnetic plates 1 held between the pole pieces 4.

The rotor 8 of the motor is rockably mounted on a bearing shaft 9centrally provided in the molding I. The proper spacing of the rotorfrom the pole faces is insured by means of a washer I0. The rotor isspidershaped, having six teeth or bars tapered towards the center. Thepole faces 4 of each magnet 3 are of substantially the 5 same width asthe Width of the spider teeth;

that is. to say, the outside pole faces are wider than the inside faces.

The clock mechanism is mounted as a separate unit on the shoulder II ofthe molding I, its

spring-pressed pawl `I2 which 'is pivoted on one of the teeth of therotor. This rotor tooth is provided also with a projection I3 which isheld for movement in one direction by an abutment Il* provided in themolding I. The clock mecha.- nism is centered around a bearing shaft I4,onev end of which has a bearing in an end plate I5, the other end ofwhich projects through another end plate I3 of the clock mechanism andcarries the usual minute hand I1 and hour hand I3. The end plates I5 andI6 are spaced from one another by means of uprights I9. Mounted on theshaft within the end plates is a bushing carrying a toothed wheel 2Iwhich is free to rotate with respect to gear wheel 22. The toothed wheelis engaged by the spring-pressed pawl I2 and may be moved thereby in onedirection and it is held in its advanced position by means of a. secondspring-pressed pawl 23 which is mounted on the end plate I5. When,therefore, the rotor 8 is moved it will rotate through the agency of thepawl I2 the toothed wheel 2|. Upon the return movement of the rotor tonormal, the wheel 2l will be held in its advanced position by means ofspring-pressed pawl 23, the pawl I2 riding over the teeth of wheel 2I.The gear wheel 22 loosely mounted on bushing 20 below Wheel 2l iscoupled with the latter through the agency of a light fiat spring 24.When the toothed wheel 2l is rotated, it will wind up the spring 24. Athird gear wheel 25 is rigidly mounted on the bushing 23 and a springclutch 23 is provided between 25 and 22. The gear 22 engages with apinion 21 mounted in an arbor 23 carried in the end plate I3. Throughthe usual gearing the arbor 28 is connected with the escapementmechanism 29. The latter may be adjusted by means of a geared segment 3Dengaging a gear wheel 3| carried by a shaft 32 which projectsthrough thecasing and may be rotated from the outside by means of a, pointer 33.`Similarly, the setting of the hands may be adjusted from outside bymeans of a knob 34 carried on a shaft 35, the lower end of which isprovided with i a gearr 36 which may be moved into engagement with agear 31 which is in engagement with the gear 25. The dial of thegclockis indicated at 33 and it will be noticed that the structure is soprovided that any size dial may be used for the same clock mechanism. I

When the electric clock is put into operation, a current of the propervoltage is supplied to it by connecting a source of power to the bindingpost 40 and to the casing 4I. As soon as this circuit is completed,current passes from the binding post 40 through the coil l6, spring 42,brush 43, cam 44, and thence through the shaft 3, and over the metallicparts of the mechanism, to housing 4I. The coil 6 being energized, amagnetic field is set up, the lines of flux of which. thread through thepole pieces 4, thereby causing them to attract the adjacent teeth of thespider 3 and rotate it in a clockwise direction, as viewed in Fig. 3,bringing the teeth more nearly into'line with the pole pieces. As therotor 3 turns against the tension of springs 45 and 46, fiat lface 41 ofonly connection with the motor being through a hook 48 of insulatingmaterial engages with the cam surface 49 of spring 42, and prevents thehook from turning around shaft 9 as a center. The hook 43 is movablymounted by means of pivot screws 53 and 5I on arm 52 which is fastenedto shaft 9. At the beginning of the rotation the flat face 41 of hook 48engages the nat cam sur- Iface 49 of the spring 42 and prevents therotation of the hook with the arm` 52 around shaft 3. The other ends ofsprings 45 and 46 are attached` to the molded part I in the mannerindicated in Fig. 1 wherein a rack 55 is provided with a number of teethprojecting within the convolutions of the spring. The spring 45 may behooked on any tooth of rack 55 to vary its tension Without interferingwith the flexibility of the rest of the spring. The other end of spring45 is fastened to hook 43 and that of spring 4B to screw 5I. y Thelatter screws into arm 52 and has a shoulder which passes throughhook'43 and limits the oscillation thereof in one direction. The resultis that the end of the hook adjacent the fiat face 41 remainssubstantially stationary because i-t is held by cam portion 43, Whilethe other end rotates with shaft 9, arm 52 and the screw 50. The arm 52displaces the pivot screw 5I in the longitudinal slot' of hook 43 untilit reaches its end position. On the other hand, the motion of the hook48 with respect to the arm 52 and pvot screw 50, is a counter-clockwiserocking motion, as viewed in Fig. 3. As the rotation of the spider 8 andarm 52 continues, the contact cam 44, which is connected through arm 52with shaft 9, gradually forces the spring 42 upwardly. In this positionthe brush 43 is still in contact with the cam 44 so that current stillflows through the winding 6, but the cam portion 49 of the spring isabout to slide over the outer end of fiat face 41 and around the arcuateportion 53 of the hook. When this point is reached, the hook, which hasbeen held back against the tension of spring 45 by the cam portion 49striking iiat face 41, is quickly snapped ahead, thereby lifting thebrush 43 from the engagement with the contact cam 44 and breaking thecircuit through coil E. During this rotational movement of the spider 8,the pawl I2 slides over the teeth of ratchet wheel 2i and as soon as thecoil 6 is deenergized, by opening of the contacts 43 and 44, the rotor 8returns to its original position under the influence of tension springs45 and 46, the ratchet wheel 2l being carried with it by action of thepawl I2 engaging with the teeth of the wheel. The spring 24 is maderelatively weak with respect to the two springs 45 and 43, so that therotor or spider isl permitted to return to its original position againstthe tension of spring 24. Just as this original position is reached, thecontact spring 42 snaps down to its normal position, and the variousoperating steps are repeated in the same manner as already described.The ratchet wheel 4I is prevented from returning to its originalposition by the holding pawl 23.

Two or more oscillating cycles of the rotor may follow in quicksuccession until the spring 24 is tensioned sufficiently tocounterbalance the tension of springs 45 and 43 and prevent the rotorfrom returning to its original position.l Spring 24 may be made so shortthat a single operation will wind it up. When this state is reached, thecommutator parts retain the position in which the brush is out ofengagement with the cam 44. In the meantime, spring 24 has been drivingthe escapemenwhand and other clock works forming the timaunit, andcontinues to drive these parts.

When the tension of spring 24 has been suilciently reduced by drivingthe clock works, the rotor and associated commutator parts return to thenormal position, thereby causing the coil to beenergized and the spring24 tensioned again to such value that lthe parts are held with thecontacts open.

I have observed in vclocks constructed in accordance with the presentdisclosure that, when current is disconnected from the coils $and therotor 8 is in its extreme counter-clockwise position (as viewed in Fig.4), the clockwork (Fig. 6) is operated by the tension primary drivingsprings 45 and 48 through the secondary driving spring 24 or 245. Thiscontinues until the rotor 8, after rotation in a clockwise direction(Fig. 4) strikes the stop I3a. From this point, spring 24a drives theclockwork until it is unwound unless, of

course, electric current is turned on in the mean- 2o time and springs45 and 46 are again placed.

46, when the clock is rst puty into operation the drive spring 24aisftensioned to a plurality of units by successive oscillations of themotor rotor and thereafter is kept tensioned by the storing of one unitat a time, responsive to singleI oscillations of the rotor. The resultof this is that if the supply current of the mo'tor is turned olf for aperiod of time greater than that necessary for the clock 40 works toexpend one unit of energy, the clock will continue to operate until allof the units of venergy are used up and the spring 24'L is totallyunwound, or until current is again supplied to the motor, whereupon thedriving spring 24*l is immediately tensioned to its full operatingvalue.

The teeth of the ratchet wheel 2| are made relatively fine so that ifthe voltage applied' to the motor is low, the rotor may turn just farenough to open the contacts 43 and 44. On low voltage therefore, thetime between oscillations of the rotor would be small, whereas if arelatively high voltage were supplied to the motor, the turning angle ofthe rotor would be large and conse quently the time between theoscillations thereof would be greater. This feature insures that thedevice will operate over a relatively wide change in supply voltage andfurthermore that shock to the parts upon the application of high voltagewill be avoided. All of the energy will be taken up by the `spring 24 or24*.

Ihe brush 43 should not disengage contact cam 44 until it is lifted freetherefrom by the point of the hook 48 sliding quickly under the camportion 49 of the spring 42. This insures that a quick break will bemade and wearing of the contact points by minute arcs prevented.Adjustment of the contact cam relative to the brush can be made byloosening the screws 50 and 5i, and moving the cam to a new position.Because of the rotary motion ofthe contact cam with respect to thebrush, a wiping action is produced which tends to keep the contactsurface clean and in efficient working condition.

When it is desired`\,to repair the commutator or to replace 'any of itsparts, the hook 48 thereof may be removed merely by unhooking thesprings 45 and 46 and removing the screws 50 and 5i. The contact cam 44may now be removed. All of these parts are located at the back side ofthe whole clock unit and so may be repaired lor adjusted withoutdisturbing the rest of the motor unit, or the time unit. The entiremotor unit may be separated from the clock merely by vunscrewing thebolts which constitute the sole means of holding together the housingscontaining the motor and the clockwork.

What I claim is:

1. In an electric clock, an electric motor comprising a stator and arotor, a clockwork comprising a toothed wheel, a pawl carried by saidrotor and engaging said toothed wheel; a housing for said motor and forsaid clockwork, a cover for said housing, and fastening means engagingsaid housing and cover constituting the sole means of holding said motorand clockwork together.

2. In an electric clock, an electric motor comprising a stator and arotor, a shaft for said rotor, a clockwork comprising a toothed wheeland a main shaft carrying the clock hands, said shafts being separatefrom one another, a spring pressed pawl carried by said rotor andengaging said toothed wheel, a housing for said motor and for saidclockwork, a cover for said housing, and fastening means engaging saidhousing and cover constituting the sole means of holding said motor andclockwork together.

3. In an electric clock, an electric motor comprising a stator and arotor, a shaft for said rotor, a clockwork comprising a toothedwheel anda main shaft carrying the clock hands, said shafts being separate fromone another, a spring pressed pawl carried by said rotor and engagingsaid toothed wheel and constituting the sole connection between themotor and the clockwork, a housing for said motor and for saidclockwork, a cover for said housing, and fastening means engaging saidhousing and cover constituting the means of ...holding said -motor andclockwork together.

4. In an electric clock, an electric motor comprising a stator and arotor, a clockwork comprising a toothed wheel, a housing for said motorand clockwork, and fastening means engaging said housing andconstituting the sole means of holding said motor and clockwork togetherin said housing.

f FRITZ LOEFFLER.

